Sound reproducer



May 14, 1929. KOLSTER 1,712,920

SOUND REPRODUCER Filed Sept. 17, 1927 2 sheets-sheet 1 IN V EN TOR.

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BY 0 L4TTORNEY .7

Patented May 14, 1929.

UNITED STATES PATENT OFFICE.

FREDERICK .A. KOLSTER, OF PALO ALTO, CALIFORNIA, ASSIGNOR TO FEDERAL TELE- GRAPH COMPANY, OF SAN FRANCISCO, CALIFORNIA, A CORPORATION OF CALI- FORNIA.

application filed September My invention relates broadly to sound reproducers and more particularly to a mounting for-a sound reproducing diaphragm of the cone type.

One of the objects of my invention is to provide a construction of free edge sound reproducing diaphragm with a suspension for said diaphragm remote from the free peripheral edge thereof.

Another object of my invention is to provide a cone shaped sound reproducing diaphragm which is unrestricted at its peripheral edge and which is suspended at points intermediate the apex and free peripheral edge thereof for permitting longitudinal vibration of the diaphragm in the direction of its apex.

A further object of my invention is to provide an arrangement of string suspension for a cone shaped sound reproducing diaphragm at a position remote from the free peripheral edge of the diaphragm.

Other and further objects of my invention reside in the arrangement of the string suspension for a cone shaped sound reproducing diaphragm, as more fully described in the specification hereinafter following by reference to the accompanying drawings wherein:

Figure 1 is a rear view of the sound reproducer of my invention; Fig. 2 is a crosssectional view through the electromagnetic sound reproducer on line 22 of Fig. l; and Fig. 3 is a front view of the sound reprodu-cer of my invention.

The conical shaped sound reproducing diaphragm employed in the sound reproducer of my invention is free at the peripheral edge thereof and is supported solely at points intermediate the apex and free peripheral edge. I provide a stretched membrane for supporting the cone shaped sound reproducing diaphragm adjacent the apex thereof in a manner more fully set forth in Letters Patent 1,637,119, dated July 26, 1927.

At points remote from the free peripheral edge of the conical shaped sound reproducing diaphragm I provide cords for steadying and centering the cone structure with respect to the frame which surrounds the cone structure. These cords are anchored at points on the frame structure and pass through the conical shaped sound reproduc ing diaphragm positioning the diaphragm in a position by which it may be moved 10n- 17, 1927. Serial N0. 220,259.

gitudinally but prevented from displacement in radial directions.

Referring to the drawings in more detail, reference character 1 designates a casing which houses a field magnet system having a pole member 2 on which is wound the field magnet 24. The pole member 2 passes through a central aperture formed in plate member 20 at the front of the casing 1. Plate member 20 is provided with flattened portions 3 at diametrically opposed points about the periphery of the plate member 20, and from these flattened portions 3 extend the radial arms 4 which connect with the rim members 5 and 6, which are suitably secured together by means of rivets 8. The rim 6 provides a seat for the felt pad 7 which may be pressed into engagement with the rear of a panel with which the sound reproducer is associated. The rim 5 has an annular flange 9 secured thereto, to which the ends of the radial arms 4 are attached. A spring fastener 10 is provided on each of the radial arms 4, each fastener being secured to a corresponding radial arm 4 by a screw member 11. The fasteners 10 are substantially in the form of clips serving to secure the ends of diametrically extending cords l2 and 14 which cross each other along the axis of the cone 30 as represented by reference character 15. The cone diaphragm 30 supports a bobbin member 21 by means of the conical member 22 which is in turn secured to the cone diaphragm through the flexible membrane 16. The flexible membrane 16 is stretched over the annular head 19 on ring member 17 and secured in place by means of the ring member 18. The bobbin support 21 carries a winding 23 which is free to move longitudinally within the gap between the pole member 2 and the plate member 20. The pole member 2 is cut away as represented at 25, enabling the cone shaped diaphragm 30 to lit snugly against the driving structure. The free peripheral edge 26 is centered within the frame structure comprising arms 4 and rim members 5 and 6 by the cords 12 and 14 in such manner that the free peripheral edge 26 is separated by a positive air gap 28 from the felt ring member 27 There is no support at the peripheral edge of the cone and the entire mass of the cone is carried at a point adjacent the apex and remote from the peripheral edge. The cords 12 and 14 serve to steady the cone and to prevent radial movement thereof while allowing free longitudinal movement. At the intersection 15 of cords 12 and 14 and at the points 31, 32, 33 and 34 where the cords 12 and 14 pass through the side walls of the cone shaped sound reproducing diaphragm a suitable glue orambroid-is provided forming an interlocking connection for preventing a slipping of the cords with respect to each other orwith respect to the material making up the cone 30.

While I have described the electromagnetic sound reproducer of my invention in certain of its preferred embodiments, I desire that it be understood that modifications may be made and that no limitations upon my invention are intended other than are phragm intermediate the apex and free pcripheral edge thereof and a pair of cord members secured at opposite ends to said frame structure and extending diametrically across said conical shapedsound reproducing diaphragm for centering said diaphragm with respect to said suspension means and preventing radial movement of said diaphragm while permitting free longitudinal vibration thereof.

2. A sound reproducer comprising a conical shaped sound reproducing diaphragm, a frame structure, a pair of cord members fastenedat' opposite ends to said frame striicture and passing diametrically through said conical shaped sound 'reproducing diaphragm and disposed at an angle with respect to each other for centering said diaphragm with respect to said frame structure.

3. A sound reproducer including a conical shaped sound reproducing diaphragm, a frame structure surrounding said diaphragm, and cord members fastened at opposite ends to said frame structure and extending diametrically through said conical shaped sound reproducing diaphragm, said cord members crossing each other in a line extending longitudinally through the apex of said conical shaped sound reproducing diaphragm and'being secured to the walls of said conical shaped sound reproducing diaphragm at positions remote from the peripheral edge thereof.

4. A sound reproducer comprising a conical shaped sound reproducing diaphragm, a frame structure, a plurality of cord members fastened at opposite ends to said frame structure and extending diametrically through said conical shaped sound reproducing diaphragm and fastened at a point along the axis of said diaphragm and secured to the material of said diaphragm at points remote from the peripheral edge of said diaphragm.

5. A sound reproducer comprising a comcal shaped sound reproducing diaphragm, a frame structure, a plurality of cord mem bers having their opposite ends fastened to said frame structure and extending radially with respect to the diameter of said conical shaped sound reproducing diaphragm, said cord members being fastened at a point along the axis of said conical shaped sound reproducing diaphragm and being secured to the material of 'said conical shaped sound reproducing diaphragm at points remote from the peripheral edge of said diaphragm.

6. A sound reproducer comprising a conical shaped sound reproducing diaphragm, a

frame structure, a pair of cord members fas- I tencd at opposite ends and extending through said conical shaped sound reproducing diaphragm at right angles to each other,

said cord members being fastened at a point lying substantially at the center of said diaphragm and being secured to the material of said diaphragm at points remote from the peripheral edge thereof.

7. In a sound reproducer a conical shaped sound reproducing diaphragm, a frame structure, a flexible membrane for suspending said conical shaped sound reproducing diaphragm at a position intermediate the apex and free peripheral edge thereof, and a pair of cord members fastened. at opposite ends to said frame structure and extending through said conical shaped sound reproducing diaphragm at right angles thereto, said cord members,being secured to each other and fastened to the material of said conical shaped sound reproducing diaphragm at points remote from the free peripheral edge thereof for centering said diaphragm with respect to said flexible membrane and said frame structure.

In testimony whereof I afiix my signature.

FREDERICK A. KOLSTER. 

